The invention relates to an apparatus and method for using angular pulses to identify the angular position of a timing disk.
It is necessary, in connection with an electronic fuel injection system, to determined the precise times of points in a cycle where fuel injection events must take place. Such an arrangement is disclosed in U.S. Pat. No. 4,284,052, in connection with a microprocessor which identifies the beginning of the fuel injection and/or ignition cycle. In order to perform its calculation, this control device requires information concerning the current status of the crank shaft which is coupled to the individual cylinders. Accordingly, the crank shaft is coupled to a timing arrangement in the form of a timing disk which has angular marks at the circumference which are read by a pulse generator so as to supply one pulse per mark.
In order to allocate the individual angular marks to a particular point in the cycle, it is necessary to assign a defined shaft position to at least one of the angular pulses, referred to as the absolute pulse. This is done by an additional identifier. To accomplish this, a code element is arranged adjacent each angular mark and the identifier has a number of code marks which are likewise read by a pulse generator to generate code pulses. By this means, each angular pulse is identified by a number of preceding code pulses.
The greatest number of code marks per code element, and thus the length of the largest code element, is defined by the number of angular marks which need to be discriminated. It has been found that an adequate number of angular marks cannot be distinguished on a timing disk having a small diameter and having the standard size teeth.